1. Field of the Invention
The invention comprises a sysstem for determining when a patient leaves the confines of a nursing home and then subsequently tracking that patient with a directional radio receiver.
2. Description of Related Art
Several efforts have been made to provide systems to monitor prison inmates, mental patients, elderly in nursing homes, individuals lost in avalanches, dogs, etc. through the use of radio transmitter and receiver systems. Many of the systems are complex and/or unreliable. In addition, several are very expensive to implement. Typical of known systems is the device described in U.S. Pat. No. 3,478,344 entitled BEHAVIORIAL SUPERVISION SYSTEM WITH WRIST CARRIED TRANSCEIVER. According to that disclosure an individual requiring supervision wears a radio on his wrist. The system detects when the supervised individual leaves the confines of a certain area.
U.S. Pat. No. 4,225,953 describes another device for pin-pointing the location of an individual in a building having a plurality of rooms. While that system appears to have the capability of determining the location of a person in a building, it does not appear to be useful for determining if an individual has left the structure.
U.S. Pat. No. 3,439,320 appears to be similar to the invention described in the foregong U.S. Pat. No. 4,225,953.
U.S. Pat. No. 4,177,465 is of note in that it describes a near-range personnel beacon locator in which the flash rate of a light emitting diode indicator is proportional to the distance that the locator apparatus is to an activated beacon.
U.S. Pat. No. 3,665,313 describes a method for identifying the location of aircraft and the like given a system in which a variety of different ground transmitters produce unique coded signals so that the aircraft can triangulate its location with respect to a specific ground transmitter.
U.S. Pat. Nos. 4,112,421 and 4,209,787 describe other methods and apparatuses for determining the location of police cars within a grid network. The power level of the signal at various different locations in the grid is used to determine the likely location of the mobile police transmitters.
U.S. Pat. Nos. 4,001,828 and 4,023,176 are of interest in that they describe beacon tracking systems in which a directional receiver is used to determine the location of a transmitted signal.
The following U.S. patents are cited as showing other systems of possible relevance: U.S. Pat. Nos. 3,046,549; 3,161,881; 3,366,958; 3,766,540; 3,868,692 and 4,021,807.
While the foregoing references may be relevant to the present invention, it is clear that none of the prior art, taken singularly or in combination, teaches, hints or suggests the very economical and dependable system taught in this disclosure.